1. Field of this Invention
This invention relates to galvanic cells (in the charged state) having lithium aluminum alloy and metal sulfide elements (electrodes) and more specifically to the production of the negative electrodes of such cells.
2. Prior Art and Related Matters
Galvanic cells of the type involved here belong to the group of high temperature cells which operate at temperatures of about 450.degree. C. In the charged state the negative electrode consists of a lithium aluminum alloy, the positive electrode of metal sulfide, usually iron sulfide, and the electrolyte of an eutectic mixture of LiCl and KCl (e.g., see U.S. Pat. Nos. 3,887,396, 3,933,520 and 3,947,291). This kind of element is best assembled in the discharged state since the negative electrode then does not need to be prepared under a protective gas. In the discharged state this electrode consists of a porous aluminum matrix and the positive electrode of a mixture of Li.sub.2 S, iron and electrolyte.
A well-known method of producing the aluminum matrix for the negative electrode is to press very fine aluminum fibers (e.g., see Argonne National Laboratory, Argonne, Ill., Progress Report ANL-77-68). Such fibers are relatively expensive and therefore not desirable for manufacturing purposes.
A cheaper method of production would be to press aluminum powder with an expanding agent. When this expanding agent is dissolved out, the desired pore structure would result. However it is well known that oxide layers inevitably form on the aluminum powder and prevent the cohesion of the pressed particles.